Abstract: Objective To investigate the effects of DL-3-n-Butylphthalide (NBP) on proliferation and apoptosis of 1-methyl-4-phenylpyridinium (MPP⁺)-induced SH-SY5Y cells, and mechanisms via mixed lineage kinase 3 (MLK3) signaling pathway.Methods The SH-SY5Y cells were divided into control group, MPP⁺ group, NBP group and URMC-099 group, that cultured normally, with 1 mmol/L MPP⁺ for 24 hours, with 10 µmol/L NBP for 3 hours and then with MPP⁺ for 24 hours, and with 200 nmol/L MLK3 inhibitor URMC-099 for 3 hours and then with MPP⁺ for 24 hours, respectively. The morphology of SH-SY5Y cells was observed under inverted phase contrast microscope and the survival rate was measured with 3-(4,5-Cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assays. The apoptosis was quantified under flow cytometry with Annexin V/PI fluorescence staining, and the nuclear morphology was observed with Hoechst 33342 staining. The expression of phosphorylated protein of MLK3 (p-MLK3), c-Jun N-terminal kinase (p-JNK), extra cellular regulated protein kinases (p-ERK1/2) were detected with Western blotting.Results Compared with the control group, the survival rate reduced and apoptosis increased in MPP⁺ group (P<0.05), with the increase of p-MLK3 and p-JNK and decrease of p-ERK1/2 d (P<0.05). Compared with MPP⁺ group, the survival rate increased and apoptosis reduced in both NBP and URMC-099 groups (P<0.05), with the decrease of p-MLK3 and p-JNK and increase of p-ERK1/2 (P<0.05).Conclusion NBP can decrease the apoptosis and promote the proliferation of SH-SY5Y cells induced by MPP⁺, which may be associated with inhibiting MLK3 signaling pathway, and regulating the downstream p-JNK and p-ERK1/2.

Key words: Parkinson's disease, DL-3-n-butylphthalide, mixed-lineage kinase 3, apoptosis, SH-SY5Y cells